The present invention relates to an artificial jointless foot having an incompressible core, preferably made of wood, the underside of which slopes upwards from the front to the rear and forms an upper connecting surface in the ankle region and extends into the instep region of the foot with a portion decreasing in height towards the front, a heel wedge connected to the underside of the core and made of soft plastic foam, and a skin-forming layer made of plastic foam and completely surrounding the arrangement comprising the core and plastic foam heel wedge, with the exception of the upper connecting surface.
An artificial jointless foot is disclosed in German Patent Specification 3,309,777. The essential advantage of this foot is that the skin-forming layer protects the inner structure against the penetration of moisture and aggressive materials. The incompressible core extends very far into the instep region and ends approximately in the ankle region of the artificial foot. Adjacent to the front side of the core there is only the skin-forming layer which determines the flexibility of the foot in the toe and ankle region, together with a sheet-like fabric insert fastened to the underside of the front edge of the core and extending to the toes. The fabric insert stabilizes the foot against twisting in the ankle region. The soft heel wedge attached under the core in the heel region is likewise enclosed by the skin-forming layer. The skin forming layer, because it is relatively hard and having a weight per unit volume of the plastic foam of approximately 6 g/cm.sup.3, should have only a small wall thickness of approximately 2 mm in the region of the heel wedge so as not to excessively impair the elastic properties of the very soft heel wedge. With this foot, the rolling action is determined first by the soft heel wedge surrounded by a relatively hard wall and then by the bending of the skin-forming layer in the ankle and toe region of the foot. The foot acquires relative rigidity because of the incompressible core extending into the ankle region.
A product catalog of Campbell Childs Inc., Phoenix, Oreg., USA, discloses a foot structure which is called the S.A.F.E. Foot and in which an incompressible core is provided in the ankle region only. An elongate inner foot extending into the toe region adjoins the front side of this core. Approximately in the region of the center of the foot, the inner foot is hollowed out on its underside, so that at this location there is an appreciable thinning of material which defines a bending region for the inner foot. The inner foot and the core, with the exception of the upper connecting surface, are surrounded by a relatively rigid foam which at the same time forms the heel wedge. Strips of elastic band extend from the core underneath the inner foot and are anchored to the inner foot at the tip thereof. A further strip of elastic band extends from the front side of the core directly into the material of the inner foot. In comparison with the foot mentioned in the introduction, this foot offers the advantage of flexibility, even in the instep region. This foot is extremely expensive due to the measures needed to stabilize the foot by means of the strips of elastic band. Furthermore, the inner structure of the foot is not protected against the penetration of water or aggressive agents.